Get a Steam Deck. Looks like Flightgear will run on them and you can use them as a portable PC when using it with a docking station.

I’m not saying this is the best choice but I went from a gaming PC to a laptop/Steam Deck and haven’t touched the PC since. Best of luck with whatever you decide.

I think it might be LXQT?

You need to theme it but depending on how you theme it you can get it looking like Win95. In fact I distinctly remember seeing Win95 themes for LXQT

https://github.com/pixelocdguy/windows-classic